Photonic crystals (PhCs) are artificially-manufactured, multi-dimensional periodic structures whose refractive index is periodically spatially modulated and the resultant photonic dispersion shows a band nature reminiscent to the electronic band structure in a solid. It has been reported that the light propagation direction in photonic crystals can become very sensitive to the incident angle and wavelength of radiation and produce “superprism” effects. Light path swings of from +70° to −70° and negative bending (i.e., negative refraction) have been observed as a result of a slight change of the incident angle of radiation from +7° to −7°.
Negative refraction in photonic crystals has been experimentally demonstrated at microwave wavelengths. The experimental demonstration of light focusing due to negative refraction by a two-dimensional photonic crystal at shorter infrared (telecommunication) wavelengths has been reported.
However, it would be desirable to have a device that can solve problems, such as control of radiation at distances that are close to the wavelength of the radiation.